Gate valve



FIG. 1 is a perspective view taken from the top, front and left side of a gate valve showing my new design;

FIG. 2 is a perspective view taken from the top, rear and right side thereof;

FIG. 3 is a bottom plan view thereof; and

FIG. 4 is a left side elevational view thereof. 

The ornamental design for a gate valve, substantially as shown and described. 